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Furring out 2x6 rafters in cathedral ceiling for spray foam

user-6988242's picture

Hello,

I need to fur out my rafters in my cathedral ceiling to at least 9 inches for insulation.  I am debating between using wood 2x6's attached to the existing 2x6 rafters with plywood gussets or using metal 2x6 studs screwd to the bottom of the rafters.  The metal studs would be easier and cheaper to attach, but I am concerned with attaching drywall and recessed light fixtures to them  Any help is greatly appreciated.  Thank you.

Alex

Alex (post #215707, reply #1 of 3)

user-6988242 wrote:

Hello,

I need to fur out my rafters in my cathedral ceiling to at least 9 inches for insulation.  I am debating between using wood 2x6's attached to the existing 2x6 rafters with plywood gussets or using metal 2x6 studs screwd to the bottom of the rafters.  The metal studs would be easier and cheaper to attach, but I am concerned with attaching drywall and recessed light fixtures to them  Any help is greatly appreciated.  Thank you.

Alex

With the plywood gussets and straight 2x6's you can correct any discrepancies in the current framing.

Using steel you'd have to shim to keep them from buckling, as well as it would be difficult to screwgun through the flange at an angle.......the screw would walk around.  Pre drill.

drywall is routinely mounted to metal, however I wouldn't use 26 gauge.  Can hangers, you can flatten out the end of the brackets to screw them to the metal.  Plastic grommets would be needed in the metal holes if you pass Romex through them.

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A thought (post #215707, reply #2 of 3)

IDEA: TJI's hung with metal hangers directly below rafters. Screw the top of the TJI into the rafter. Metal support brakets ensure that loads are not totally transfered to the existing rafters. If the cross-room span is not too great, consider installing the TJIs at 90 degrees to existing rafters. Use metal TJI hangers and tie TJIs to rafters with screws. Now insulate the existing rafters in one direction and the TJIs in the other. CAUTION: If you use batt insulation, consider how each rafter bay is vented. If you spray insulation into the existing rafter pocket (or fill the void with tightly-fitted insulating foam boards, you need not worry about moisture accumulation below the roof deck.

Mel Fros froscarpentry.com

Thankyou for the ideas.  If (post #215707, reply #3 of 3)

Thankyou for the ideas.  If my rafters are staight and in plane with each other, I am thinking I will just screw the metal studs (2x6,20g) to the bootom of the rafters.  If there are discrepencies, I like the idea of correcting them by using plywood gussets to hold the new 2x6's at the proper height.   I could shim the tgis as well, but it will cost a lot more.   I need to pull some stings and see how my rafters look.  Hopefully there is no sag  and they are staight.   My insulation will be 2 inches of closed cell foam followed by 7 inches of open cell.  Thanks again.

Alex